[Albert] read the Cisco PIX Wiki, and discovered that the motherboard of the PIX 506E is the same as the PIX 525, which has a 600Mhz Coppermine Pentium III CPU. So he took his Cisco PIX 506E and upgraded it by swapping out the Celeron 300Mhz, with a Pentium III 600Mhz and populating the second PC100 RAM slot inside. The system only shows 448Mhz instead of 600Mhz, but it does recognize the PIII, and there are no problems.  The CPU load has dropped to 0% after the CPU swap, and RAM upgrade.